Ring compounds comprising an inorganic atom in association with a diketonate structure are known. For example, some, such as boron diketonates, are known to be useful as electron accepting sensitizers in electron donating photoconductive compositions. On the other hand, others such as tin and copper diketonate compounds have no practical utility in sensitizing electron donating photoconductors.
Brown and Bladon describes the synthesis of three different phosphorous diketonate compositions in their publication "Synthesis of Tetrafluoro(pentane-2,4-dionato)phosphorous(V) and Analogous Compounds" appearing in Chemical Communications of 1966, page 304. However, this method is useful in making only a limited number of compounds. For example, the method does not describe the preparation of methine dyes having a phosphorous diketonate component.
Commonly assigned, U.S. patent application Ser. No. 279,365 filed July 1, 1981 by Detty et al, now U.S. Pat. No. 4,365,016, closes telluropyrylium compounds which include a tetrafluorophosphorous diketonate component for use in improving the quantum efficiency and sensitivity of electron donating photoconductive compositions. However, this application does not describe a method that could be used to make tellurium-free phosphorous diketonates.
Although boron diketonate compounds do improve the quantum efficiency and the sensitivity of electron donating photoconductive compositions above about 600 nm in wavelength, the resultant quantum efficiency and photosensitivity could be improved.